1. Field of the Invention
This disclosure relates generally to a hoisting apparatus and method and, particularly, to a hoisting apparatus and a method for hoisting a counterweight of a conveyor belt in a conveyor system.
2. Description of Related Art
Conveyor systems are used in many industries to facilitate handling of items or materials. In particular, conveyor systems are useful in transporting heavy or bulky materials over fixed distances where the use of human labor or other types of machinery is laborious and/or expensive. Due to the speed and efficiency of transport, conveyor systems are widely used in material handling industries, such as handling of mining or agriculture materials. Conveyor systems in the material handling industries may be used, for example, to transport excavated materials in an above-ground mine from an excavation site to a remote location for further processing, storage, or transport. Such conveyor systems utilize a continuously moving belt that is driven by one or more pulleys.
The conveyor system used for transporting excavated materials is often the lifeline in mine operation. Because proper functioning of the conveyor system is required for carrying excavated materials from the excavation site, regular inspection and maintenance of the conveyor components are essential. While certain conveyor inspection and maintenance processes can be carried out while the conveyor is running, such as lubricating the bearings, other processes can be performed only when the conveyor system is shut down. Due to the importance of a working conveyor system in transporting excavated materials, it is important to minimize the time that the conveyor system is shut down and perform the inspection and maintenance processes as quickly and efficiently as possible.
One inspection and maintenance process that may require stopping the conveyor system relates to the servicing or adjustment of the conveyor counterweight. In general, the conveyor counterweight is used to adjust the tension of the conveyor belt. Proper tensioning of the conveyor belt is important because it avoids damage to the conveyor belt and prevents premature wear of the conveyor system components. Typically, tensioning of the conveyor belt is effected by moving a pulley attached to a counterweight assembly by gravity. The conveyor belt wraps around the pulley. Moving the pulley in one direction increases the tension in the conveyor belt, while moving the drum in the opposite direction reduces the tension in the conveyor belt. Because the conveyor systems used in transporting excavated materials are designed to transport many tons of excavated materials, heavy counterweights, weighing 2,000 to 100,000 pounds or more, are used to maintain the proper tension in the conveyor belt.
In certain situations, the heavy counterweight must be moved to facilitate servicing of the conveyor system. Due to the size and weight of the counterweight, specialized equipment, such as a heavy-duty crane, must be brought to hoist the counterweight. The crane is positioned proximate the counterweight such that it can be temporarily hoisted from its initial location.
The conventional procedure for hoisting the conveyor counterweight by crane has several disadvantages. Such procedure complicates the servicing process by requiring additional specialized equipment and personnel trained to safely operate the equipment. This increases the servicing cost and the time during which the conveyor system is out of operation. Often, the entire mining site must be shut down because excavated materials cannot be carried away.